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DIPOL Weekly Review - TV and SAT TV, CCTV, WLAN

No. 16/2009 (April 20, 2009)

WiMAX - are there any prospects for success? Everything shows that this year will be decisive for selecting technology for 4G wireless systems. Wireless networks of the Fourth Generation should provide mobile data transmission at speeds of 100 Mbps - to fast-moving terminals - and 1 Gbps in the case of relatively fixed positions of the terminals. Currently the development of mobile technologies for 4G goes two ways, WiMAX and LTE. WiMAX technology is more advanced in terms of implementation. However, it lacks a major marketing success which could persuade manufacturers to start production of new, cheaper devices. The concept of building all-American 4G networks based on WiMAX - first pushed by Sprint company, then developed as a common project with Clearwire - still faces difficulties. Despite the expenditure of 3 billion dollars, the service has so far been launched only in Baltimore and Portland. The companies announced to include another 10 cities this year. However, there are new disturbing facts - at the end of last year Alcatel-Lucent abandoned development of solutions based on WiMAX technology, in January this year Nokia stopped work on WiMAX devices as well. According to vice-president Anssi Vanjoki from Nokia, LTE technology is more promising. LTE (Long Term Evolution) is being developed to improve the Universal Mobile Telecommunications System (UMTS). LTE is to increase the performance of the 3G UMTS packet service (based on TCP/IP protocol), with data rates over 100 Mbps. It has been adopted as a 4G standard by AT&T, Telstra, Vodafone, China Telecom, T-Mobile, and Verizon yet. In January this year, an agreement was signed between Ericsson and TeliaSonera to launch commercial LTE network in Stockholm. In early February 2009, Motorola started the first test 4G network using LTE technology in Swindon, UK.

At CeBIT 2009, the only exhibit concerning LTE technology was ... the poster at Alcatel stand. Lack of sufficient funds for investments in new technologies may stop development of both WiMAX and LTE.

Image quality of HDTV broadcasts. The basic parameters that determine image quality of TV broadcasts are resolution, number of frames/images per second, and scanning method. Standard television (SDTV) in PAL system uses 625 lines, having 576 active (visible) lines. The corresponding numbers in NTSC are 525 and 480. There are two possible modes of scanning (and displaying): "i" - interlaced, and "p" - progressive. In "i" mode, one field is made of even lines (i.e. 2, 4, 6 etc.), the next one of odd lines (1, 3, 5 and so on). In "p" mode all lines are being scanned one after another.

PAL can be described as 576i50 system (576 active lines, "i" mode of scanning, 50 Hz). To sum up - even lines take first 1/50 s, and odd lines take another 1/50 s. The effect of such operation is 25 frames per second. HDTV offers resolutions 720p, 1080i, and (prospective) 1080p (1080p/24 - Full HD option - is employed by Blu-ray technology). Considering the first two alternatives, 720p resolution provides images of higher quality (sharpness, details) than 1080i. The last number is rather a mixture of sales gimmick and technical oversimplification. The 1080i is made of two fields, 540 lines each, being displayed by turns, correspondingly the even and odd lines. So we have 1080 lines, but displayed alternately, which gives 50 fields with 540 lines per second, whereas 720p system provides 50 complete frames having 720 lines with the fewest image artifacts. Generally, progressive scanning is recognized as the ultimate solution. SDTV transmissions can have both 4:3 and 16:9 aspect ratio. HDTV broadcasts are prepared for 16:9 screen format.

Quality of multiswitches - isolation between inputs. Isolation between inputs of a multiswitch is one of the crucial parameters that determine its quality. It is a factor which distinguishes class of the multiswitch. Good isolation (>30 dB) ensures that interferences coming from other inputs do not influence useful signals. In the case of poor isolation the interferences cause increase of BER and may block reception of signals with lower levels. Some transponders can be received properly, but others are inaccessible - the receiver displays information like "no signal".

The market leader in this field is TERRA, with its top-class multiswitches. The manufacturer guarantees isolation not less than 30 dB, but the measured values reach 40 dB. Due to high quality components and special design, these multiswitches allow to build very large installations. They permit to use high input levels - for example, 80 dBuV from the Quatro LNB. With 40 dB isolation the interference will be below 40 dBuV (80 dBuV - 40 dB = 40 dBuV). It will not influence reception quality, as the sensitivity of a typical receiver is 45 dBuV.

TERRA multiswitches of MSV series allow to build SMATV systems with 200 - 300 outlets. Aside from superb isolation, the multiswitches have been equipped with cable loss correction. This correction compensates for different signal attention (depending on frequency), equalizing signal levels within whole frequency band.

ULTIMAX - monitoring of banks. Tejarat Bank, one of the largest banks in Iran, has chosen digital video recorders from the leader in implementing H.264 compression - HikVision company. On the European market the DVRs are sold as ULTIMAX. According to the opinion of one of Tejarat Bank managers, the choice was motivated by compliance with all bank's requirements. They included high image parameters (4CIF resolution), system stability, and overall reliability. The latest implementation of MPEG4 compression - H.264 ACE (Advanced Code Efficiency) - and DSP processors from Texas Instruments enable online monitoring of all branch offices and agencies. Online monitoring is a distinctive feature of the system, as the bank has over 2000 such outlets located in several larger cities like Masha, Rasht, Esfehan, Shiraz. It is necessary to control all the places in real time. The focus is on security of the staff, of the deposits, as well as on maintaining the highest standards of customer service. Remote online monitoring allowed to create an appropriate unit responsible for investigating the situation at any moment and taking quick decisions in emergency cases. The preview of the images is conducted in the monitoring center based on a number of servers. The current version of network client application enables one server to manage up to 50 DVRs.

One of the branches of Tejarat Bank in Iran

Efficient transmission of video and audio streams - the use of multicast VPN tunnel. The increasing interest in broadcasting video on the Internet puts high demands on link capacity. Multicast can be the basis for the development of efficient, distributed applications, where transmission is performed from one sender host to multiple recipients (clients). Multicast allows to send a single stream of data to a group of clients, without the necessity of providing a separate stream for each client. In this way, even increasing the number of clients, the occupied bandwidth is the same. A major obstacle to a widespread use of the advantages of multicast is the lack of multicast mode in network routers. Currently, multicast is practically limited to single local networks. The restrictions can be circumvented by some intermediate solutions - building on the Internet VPN tunnels which allow to create private networks linking all locations where there is a need of monitoring the transmitted video. In this way, only one stream is transmitted over the Internet, regardless of the number of connected clients. This reduces the cost of the service, because it does not need to provide high bandwidth. At the same time it can increase the quality of the image, because the single stream can be adjusted to the capacity of the link. The condition for multicast is support of IGMP (Internet Group Management Protocol) routing protocol by the sender host (e.g. IP camera) and intermediate switches and routers. This function is available in ACTi IP cameras and video servers, ULTICAM IP cameras, ULTINET video servers, and ULTIMAX DVRs.

The difference in transmitting signals with Unicast and Multicast routing

Use of multicast and VPN tunnel to transmit video stream on the Internet

Color adjustment in ACTi cameras. White balance (WB) function allows to adjust reproduction of colors in relation to the white reference. ACTi cameras have 6 modes of white balance (AUTO, INDOOR 1, INDOOR 2, OUTDOOR 1, OUTDOOR 2, HOLD CURRENT, MANUAL). In AUTO mode the white reference is the brightest point of an image, which is sufficient in majority of applications. However, especially with PTZ cameras, there can be areas where such point is far from white, which causes false colors of the image. Given such difficulties, it is possible to save WB settings in a special manner (HOLD CURRENT). In this mode the user "learns" the camera to "recognize" white color. The most precise adjustment is possible in MANUAL mode, suitable for special applications and advanced users. It allows to modify red and blue components of the image (in comparison with green level). In addition, the user can choose predefined color settings corresponding to artificial (INDOOR 1, 2) or natural light (OUTDOOR 1, 2).

Proper white balance

Improper white balance

How to increase throughput of wireless links - packet aggregation in ULTIAIR devices. The 802.11 standard protocol does not guarantee efficient work with a large number of packets. It is especially visible in large networks. In this case, the solution is "packaging" of the packets. This process is commonly called packet aggregation. It consists in combining a large number of small packets into larger units, in order to increase the efficiency of the entire link. Aggregation of packets allows to increase channel throughput even up to 5 MBps. So far, this function was available in a small group of advanced devices, e.g. TSUNAMI.ULTIAIR devices have also been equipped with this technology. By default, this option is not active, so the user should switch it on in the device settings.NOTICE! To get correct transmission, packet aggregation function must be enabled on both devices working together as Point to Point link.

Diagram showing application of ULTIAIR devices in city monitoring system. Due to the special features described above, the system is capable of smooth transmission of video streams from IP cameras to remote monitoring center.

Wireless data transmission over long distances using ULTIAIR devices. A major problem in constructing long-distance links is to obtain high data speeds. In point-to-point connections, it is possible to reach up to 23 Mbps in each direction. However, with growing distance the signal level decreases, which limits the speed of transmission. The solution to this problem would be use of intermediate points through which the total distance is divided into several smaller ones. The use of several shorter links allows to get higher transmission speeds.

In the diagram above, the application the intermediate points allows to bypass the area where the buildings would be an obstacle to radio waves.

The factors that influence the capacity of a link with intermediate point/s:

operation of other wireless networks (interference from neighboring channels),

weather conditions, especially humidity,

visibility areas of individual nodes,

other factors influencing propagation of electromagnetic waves.

We have written about:

Weak GSM signal inside building? - Use GSM repeater. GSM repeaters allow to use cellular phones in locations where the range of a cellular network is sufficient for outdoor operation, but the signal is too low for connections inside buildings... - archive DWR of March 9, 2009

Recording of road traffic with the use of ULTIAIR devices and IP CCTV cameras from ACTi. Failing to yield right of way and going over a red light at the crossroads are important reasons of collisions and accidents in large cities. It is often difficult to establish the fault of the driver who caused the collision, especially when there are no witnesses available. These problems can be solved with IP video surveillance systems using wireless transmission technology that allows to deploy camera points anywhere in the city... - archive DWR of Feb. 23, 2009

Optimum cabling solutions (S/MATV) for multi-family buildings. Cabling is the part of signal distribution system in a building that is extremely difficult to exchange. In practice, it often cannot be easily modified even if the cables are arranged in tubes. So it is important to design the cabling in such a way that allows possible extension of the distributing system without a need of modifying the cable layout. If, for economical reasons, the first stage includes only MATV distributing system, the cabling should be prepared for future introduction of satellite signals... - archive DWR of Oct. 13, 2008